<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>box-model</title>
    <style>
      * {
        padding: 0;
        margin: 0;
      }
      .layout {
        height: 200px;
      }
      .box {
        height: 200px;
      }
      .left {
        float: left;
        width: 300px;
        background: #eee;
      }
      .center {
        float: left;
        width: calc(100% - 300px - 300px);
        background: #f00;
      }
      .right {
        float: right;
        width: 300px;
        background: #eee;
      }
    </style>
  </head>
  <body>
    <section class="layout float-model">
      <article class="box left">1</article>
      <article class="box center">2</article>
      <article class="box right">3</article>
    </section>
  </body>
</html>
